Doug S (foo.delete@this.bar.bar) on November 17, 2020 12:21 pm wrote:
> Dummond D. Slow (mental.delete@this.protozoa.us) on November 17, 2020 11:18 am wrote:
> > Which also tells you where the biggest threat from Apple is. It pretty much caught
> > up with state of the art x86's single core performance AND has process advantage.
> > It could shoot ahead in performance in two areas if it chose to:
> > 1) SMT as discussed. Not having SMT leaves massive multithread performance
> > gains (end energy efficiency gains, more importantly) on the table.
>
>
> Does that really matter all that much for desktop use? Maybe it matters for
> the Mac Pro, but that's just not a big enough piece of the overall Mac market
> (let alone the overall 'Apple SoC' market) for them to add SMT, IMHO.
>
> Now if Apple was going build their own servers (for iCloud, Siri, maybe Search if antitrust issues
> force Google to quit paying Apple for being the default search in Safari) then adding SMT would
> make more sense since they can amortize the extra design/verification work across more units.
>
>
> > 2) AMD and to a bit less degree Intel squeeze the single core
> > frequency of the core during single-thread boosting,
> > with very high voltage and advanced power management so that
> > they can pretty much run it as fast as the silicon
> > allows and as high or even higher than manual overclocking can reach. This is why the power consumption in
> > their single core turbo boosts is so high (it does dial way lower during all-core load clocks).
> > Apple seems to only have simple turbo that drops clocks a bit
> > on multicore load, but it is only a small difference.
> > That implies Apple could extract a lot of frequency if it
> > went as advanced on power management and aggressive
> > on turbo as AMD does. I don't know how high it could go - the low power it exhibits suggest there is a lot
> > of headroom, but perhaps the wide engine just couldin't handle much more due to timing even if it doesn't
> > have high power output. But some potential Apple has not tapped yet is likely there.
>
>
> I agree that Apple clearly has some room to increase performance with binning/turbo, but again how much
> sense does that effort make for their market? It would be nice for those of us watching on the sidelines
> and wanting to see a real performance war, but in reality Apple is competing with the last version of
> their own products not with what you can buy from Dell, and the M1 is already faster for ST than any
> x86 Mac so they don't NEED to do this. Maybe they will explore it in the M2 or M3, I hope they do, but
> I wouldn't be surprised if they feel their design effort is better spent elsewhere.
>
> Heck, Apple could get faster by simply not designing for low power. According to TSMC using HPC cells
> gets you a 10% boost, and other tricks you can do when power draw is less important can get 10% more.
> An M1+ clocked at 3.8 GHz would be one hell of a beast, though if it used 2x more power per core it
> would really only be appropriate for a Mac Pro - every other Mac is quite cooling constrained due to
> the form factor. Sure, they COULD pay for a separate tapeout when the Mac Pro starts at $5K, but they'd
> only be able to fit half as many cores at the same power budget. So they probably will use low power
> transistors there despite the potential for faster ST performance, EVEN if they do a separate design
> for the Mac Pro (i.e. based on being able to leverage it for internal server use also)

Doug is right. The value of multi-threading is workload dependent.